SCULPTING: Is it possible to keep base mesh vertices in place while subdividing?
In addition to what Mr Zak mentioned, you could try:


Both Subdivision Surface and Multiresolution have a Simple option,
when you turn it on, each subdiv will add vertices between already
existing ones without averaging the general shape. 
Secondly you could make a
copy of a basemesh, then add ShrinkWrap modifier on the mesh you will
subdivide and pick the copy as a target. This way you will keep the
mesh shape the way you want it. Both copy and subdivided mesh must be in the same location.